| Summary: | Wild tobacco species in the <i>Nicotiana</i> section <i>Suaveolentes</i> are promising genetic resources to introduce their disease resistance to cultivated tobacco, <i>Nicotiana tabacum</i>. However, hybrid lethality is observed in hybrid seedlings from crosses between most <i>Suaveolentes</i> species and <i>N. tabacum</i>. In particular, <i>N. benthamiana</i> belonging to the section <i>Suaveolentes</i> produces only viable hybrids after crossing with <i>N. tabacum</i>. In the present study, crossability between <i>N. benthamiana</i> and <i>N. excelsior</i> (section <i>Suaveolentes</i>) was investigated to test the possible usefulness of <i>N. benthamiana</i> as the bridge parent to transfer desirable genes of <i>N. excelsior</i> to <i>N. tabacum</i> via bridge crossing. After reciprocal crosses using three accessions of <i>N. benthamiana</i> and <i>N. excelsior</i> each, several crossing barriers such as cross-incompatibility, seed abortion, and male and female hybrid sterility were observed. Although reciprocal hybrids between <i>N. benthamiana</i> and <i>N. excelsior</i> showed a high degree of chromosome pairing in meiosis, univalents and multivalents, as well as chromosome bridges and lagging chromosomes, were observed. These meiotic abnormalities were thought to cause hybrid sterility. The possible usefulness of reciprocal hybrids between <i>N. benthamiana</i> and <i>N. excelsior</i> is discussed.
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